Document 112262

MDHS
Methods for the Determination of
Hazardous Substances
Health and Safety Laboratory
46/2
Platinum metal and
soluble platinum
compounds in air
Laboratory method using electrothermal
atomic absorption spectrometry or
inductively coupled plasma-mass
spectrometry
December 1996
INTRODUCTION
Note 1: This method updates and replaces MDHS 46.1 The
principal changes which have been made are (i) to
recommend the use of filters that are soluble using the
dissolution technique described for platinum metal, and (ii)
to describe the use of inductively coupled plasma-mass
spectrometry for the analysis of sample solutions with a
low platinum concentration.
5 A maximum exposure limit, 8-hour time-weighted
average reference period, is proposed for halogeno­
platinum compounds:
Halogeno-platinum compounds (as Pt)
0.002 mg m-3
This limit will be published in Schedule 1 of the COSHH
(Amendment) Regulations 19964 and in Table 1 of HSE
Guidance Note EH 40,3 and will come into effect in
January 1997.
Occurrence, properties and uses
1 Occurrence, properties and uses of platinum metal and
soluble platinum compounds are fully covered in HSE
Guidance Note EH 65/24.2
Effects on health
2 The health effects of platinum metal and soluble
platinum compounds are reviewed in HSE Guidance Note
EH 65/24.2
Health and safety precautions
3 A high standard of control is required when handling
soluble platinum compounds as they are potent skin and
respiratory sensitisers. Appropriate protective clothing and
approved eye protection should be worn to prevent contact
with these compounds. Exposure by inhalation to dust,
spray or mist should be controlled by local exhaust
ventilation. Respiratory protective equipment might also be
needed when local exhaust ventilation is inadequate.
Exposure limits
4 The Health and Safety Commission has approved an
occupational exposure standard, 8-hour time-weighted
average reference period, for platinum metal:
Platinum metal
5 mg m-3
This limit is published in Table 2 of HSE Guidance Note
EH 40.3
Note 2: Halogeno-platinum compounds are co-ordination
compounds in which platinum is directly co-ordinated to
one or more halide (ie fluoride, chloride, bromide or
iodide) ions. For substances which contain platinum and
halide ions, but in which the halogen is not directly linked
by a bond to the platinum, the occupational exposure
standard for soluble platinum compounds is applicable
(see paragraph 6).
6 An occupational exposure standard, 8-hour timeweighted average reference period, is proposed for other
soluble platinum compounds:
Platinum compounds, soluble, except
halogeno-platinum compounds (as Pt)
0.002 mg m-3
This limit will be published in Table 2 of HSE Guidance
Note EH 40,3 and it will also come into effect in January
1997.
Analytical methods
7 This is not a ‘reference’ method in the strict analytical
sense of the word. There are frequently several
alternative methods available for the determination of a
particular analyte. With the exception of a few cases,
where an exposure limit is linked to a specific method
(eg rubber fume or asbestos), the use of methods not
included in the MDHS series is acceptable provided that
they have been shown to have the accuracy and reliability
appropriate to the application.
1
8 This method has been validated5 to demonstrate that
it complies with the General requirements for the
performance of procedures for the measurement of
chemical agents in workplace atmospheres described by
the Comité Européen de Normalization (CEN) in
European Standard EN 482.6 If an alternative method is
used it should also meet these performance
requirements.
hazardous to health which are present in workplace air.
The objective of air monitoring is usually to determine
worker exposure, and therefore the procedures described
in this method are for personal sampling in the breathing
zone. The method may be used for background or fixed
location sampling, but it should be recognised that, due to
aerodynamic effects, samplers designed for personal
sampling do not necessarily exhibit the same collection
characteristics when used for other purposes.
Requirements of the COSHH Regulations
METHOD PERFORMANCE
9 The Control of Substances Hazardous to Health
(COSHH) Regulations7 require that employers make an
assessment of the health risk created by work involving
substances hazardous to health, and to prevent or
control exposure to such substances. The COSHH
Regulations also include a requirement that persons who
may be exposed to substances hazardous to health
receive suitable and sufficient information, instruction
and training. Employers must ensure that their
responsibilities under the COSHH Regulations are
fulfilled before allowing employees to undertake any
procedure described in this method. Guidance is given in
the Approved Codes of Practice for the Control of
Substances Hazardous to Health, the General COSHH
ACOP, and the Control of Carcinogenic Substances, the
Carcinogens ACOP, which are included in a single
publication with the COSHH Regulations.8
SCOPE
Applicability
10 This MDHS describes methods for determination of
the concentration of platinum metal and soluble platinum
compounds in workplace air using electrothermal atomic
absorption spectrometry or inductively coupled plasmamass spectrometry. The majority of insoluble platinum
compounds in industrial use or occurring in workplace air
are also determined by the method for platinum metal.
11 The method described does not distinguish between
halogeno-platinates and other soluble platinum
compounds. Therefore when there is mixed exposure to
halogeno-platinates and other soluble platinum
compounds, the convention is that all platinum measured
is assumed to derive from halogeno-platinates, and
control to the requirements of the maximum exposure
limit for halogeno-platinates is necessary.
Effectiveness of sample dissolution procedures
0.07 M hydrochloric acid leach procedure for soluble
platinum compounds
13 The effectiveness of the 0.07 M hydrochloric acid
leach procedure for soluble platinum compounds was not
tested (see note 4).
Note 4: The 0.07 M hydrochloric acid leach procedure
used in the previous version of MDHS 461 has been
retained for continuity. It has its origins in an earlier
method for soluble lead, which uses 0.07 M hydrochloric
acid to simulate stomach acid. This approach was devised
because inhaled particles that deposit in the upper
respiratory tract are transferred to the digestive tract by
ciliary action. Any substance that is soluble in stomach
acid is therefore likely to be absorbed. Although this is a
reasonable way to look at things for a systemically toxic
substance, it is not really appropriate if the principal cause
for concern is respiratory sensitisation, as is the case for
halogeno-platinates. However, in the microgram amounts
collected in air samples, soluble platinum compounds
should be no more or no less soluble in 0.07 M
hydrochloric acid than in water, so it was concluded that it
was unnecessary to modify or test the sample dissolution
method in revising MDHS 46.
Aqua regia method for platinum metal
14 The effectiveness of the 50% (v/v) aqua regia
dissolution procedure described in MDHS 46 was tested5
on a commercially available platinum metal powder of
particle size 0.27 µm to 0.47 µm and was found to be fully
effective.
Detection limits
12 The method for soluble platinum compounds has
also been shown5 to be suitable for use with sampling
times in the range 30 minutes to 8 hours for analysis by
inductively coupled plasma-mass spectrometry; and for
sampling times in the range 4 hours to 8 hours for
analysis by electrothermal atomic absorption
spectrometry. The method for platinum metal is suitable
for use with sampling times in the range 30 minutes to
8 hours using either analytical technique.
Note 3: HSE Guidance Note EH 429 advises employers
about how they should conduct investigations into the
nature, extent and control of exposure to substances
2
15 The qualitative and quantitative detection limits for
platinum, defined as three times and ten times the
standard deviation of a blank determination, have been
determined5 to be 3.6 ng ml-1 and 12 ng ml-1 for
electrothermal atomic absorption spectrometry; and
0.003 ng ml-1 and 0.010 ng ml-1 for inductively coupled
plasma-mass spectrometry. For an air sample volume of
30 litres and a sample solution volume of 10 ml this
corresponds to platinum in air concentrations of
0.001 mg m-3 and 0.004 mg m-3 for electrothermal atomic
absorption spectrometry; and 0.001 µg m-3 and 0.003 µg m-3
for inductively coupled plasma-mass spectrometry.
Overall uncertainty
16 Laboratory experiments5 indicate that the analytical
method does not exhibit significant bias. The mean
analytical recovery for 80 spiked filters in the range
0.096 µg to 3.84 µg of platinum was determined to be
102.3% using electrothermal atomic absorption
spectrometry; and the mean analytical recovery for 110
spiked filters in the range 0.012 µg to 3.84 µg of platinum
was determined to be 100.3% using inductively coupled
plasma-mass spectrometry.
17 The component of the coefficient of variation of the
method that arises from analytical variability, CV(analysis),
has been determined5 to be less than 17% for samples in
the range 0.096 µg to 0.96 µg and less than 7% for
samples in the range 0.48 µg to 3.84 µg using
electrothermal atomic absorption spectrometry; and less
than 4% for samples in the range 0.012 µg to 3.84 µg
using inductively coupled plasma-mass spectrometry.
18 The overall uncertainty of the method, as defined by
CEN,6 has been estimated5 assuming that the flow rate is
controlled to within ±5% of the nominal value, that the
coefficient of variation that arises from inter-specimen
sampler variability, CV (inter), is negligible and that the
sampler bias is less than ±10%. It was found to be less
than 46% for samples in the range 0.096 µg to 0.96 µg
and less than 29% for samples in the range 0.48 µg to
3.84 µg using electrothermal atomic absorption
spectrometry; and less than 24% for samples in the range
0.012 µg to 3.84 µg using inductively coupled plasmamass spectrometry. The overall uncertainty of the
inductively coupled plasma-mass spectrometry method is
therefore within the specifications prescribed by CEN6 for
measurements for comparison with limit values, ie <50%
for measurements in the range 0.1 to 0.5 times the limit
value and <30% for measurements in the range 0.5 to 2.0
times the limit value. The electrothermal atomic absorption
spectrometry method only meets the CEN specifications
when the sampling time is between 4 hours and 8 hours.
Interferences
19 Electrothermal atomic absorption spectrometry is
performed at a wavelength of 265.9 nm with a solid
pyrolytic graphite platform mounted in a pyrolyticallycoated graphite tube. No interferences specific to the
determination of platinum are documented for
electrothermal atomic absorption spectrometry.
0.07 M hydrochloric acid and agitated by mechanical
shaking or using an ultrasonic bath. The leach solution is
then filtered under suction through a mixed cellulose ester
filter of 0.8 µm mean pore diameter and diluted to 10 ml.
The resultant solution is analysed by either electrothermal
atomic absorption spectrometry or inductively coupled
plasma-mass spectrometry. If platinum metal is also to be
determined, the secondary filter used for filtration of the
leach solution is kept for further treatment.
23 If platinum metal is to be determined, the sample filter
and the secondary filter used for filtration of the leach
solution (if applicable) are placed in a 50 ml beaker and
treated with 10 ml of 50% (v/v) aqua regia. The beaker is
heated on a hotplate to dissolve the filters, and the
resultant solution is then evaporated to dryness. The
residue is redissolved in 2 ml of concentrated hydrochloric
acid and evaporated to dryness twice more. Finally, the
residue is redissolved in 0.07 M hydrochloric acid and
analysed for platinum by either electrothermal atomic
absorption spectrometry or inductively coupled plasmamass spectrometry.
REAGENTS
24 During the analysis, use only reagents of recognised
analytical grade. Use only distilled or de-ionised water, or
water of equal purity (paragraph 25). Do not pipette by
mouth.
Water
25 Water complying with the requirements of BS 397810
grade 2 water (electrical conductivity less than 0.1 mS m-1
and resistivity greater than 0.01 MΩ.m at 25°C).
Hydrochloric acid (HCl), concentrated, ρ about
1.18 g ml-1, 35% (m/m) to 38% (m/m)
26 The platinum concentration of the acid shall be less
than 1.0 ng ml-1.
WARNING - Concentrated hydrochloric acid is corrosive
and the fumes are irritant. Avoid exposure by contact with
the skin or eyes, or by inhalation of fumes. Personal
protection (eg gloves, face shield or safety spectacles etc)
should be used when working with concentrated or diluted
hydrochloric acid, and sample dissolution with hydrochloric
acid should be carried out in a fume cupboard.
Hydrochloric acid (HCl), 0.07 M
20 For analysis by inductively coupled plasma-mass
spectrometry, the recommended and most abundant
isotope of platinum is mass 195. There are no isotopes of
other metals occurring at this mass, and the only
documented potential interferent is 179hafnium oxide.
27 Carefully add 5.8 ml of concentrated hydrochloric acid
(paragraph 26) to 500 ml of water (paragraph 25) in a
1000 ml volumetric flask. Dilute to the mark with water and
mix thoroughly.
PRINCIPLE
Hydrochloric acid (HCl), diluted 1 + 1
21 A measured volume of air is drawn through a filter
mounted in an inhalable dust sampler.
28 Carefully add 500 ml of concentrated hydrochloric acid
(paragraph 26) to 450 ml of water (paragraph 25) in a
2 litre beaker. Mix, allow to cool and quantitatively transfer
to a 1000 ml volumetric flask. Dilute to the mark with water
and mix thoroughly.
22 If soluble platinum compounds are to be determined,
the filter and collected sample are treated with 5 ml of
3
Nitric acid (HNO3), concentrated, ρ about 1.42 g ml-1,
69% (m/m) to 71% (m/m)
Working standard platinum solution, 100 µg ml-1 of
platinum
29 The platinum concentration of the acid shall be less
than 1.0 ng ml-1.
34 Accurately pipette 10 ml of stock platinum standard
solution (paragraph 32 or 33) into a 100 ml volumetric
flask. Carefully add 10 ml of concentrated hydrochloric
acid (paragraph 26), dilute to the mark with water
(paragraph 25), stopper and mix thoroughly. Prepare this
solution fresh weekly.
WARNING - Concentrated nitric acid is corrosive and
oxidising, and nitric acid fumes are irritant. Avoid
exposure by contact with the skin or eyes, or by inhalation
of fumes. Personal protection (eg gloves, face shield or
safety spectacles etc) should be used when working with
concentrated or diluted nitric acid, and sample dissolution
with nitric acid should be carried out in a fume cupboard.
Nitric acid, diluted 1 + 9
30 Add approximately 800 ml of water (paragraph 25) to
a 1 litre volumetric flask. Carefully add 100 ml of
concentrated nitric acid (paragraph 29) to the flask and
swirl to mix. Allow to cool, dilute to the mark with water,
stopper and mix thoroughly.
Aqua regia, 50% (v/v)
31 Add approximately 400 ml of water (paragraph 25) to
a 1 litre volumetric flask. Carefully add 125 ml of
concentrated nitric acid (paragraph 29) to the flask and
swirl to mix. Carefully add 375 ml of concentrated
hydrochloric acid (paragraph 26) to the flask and swirl to
mix. Allow to cool, dilute to the mark with water, stopper
and mix thoroughly.
Stock standard platinum solution, 1000 µg ml-1 of
platinum
32 Use a commercially available standard solution at a
concentration of 1000 µg ml-1 of platinum. Observe the
manufacturer’s expiry date or recommended shelf life.
Alternatively prepare a stock platinum standard solution
by the following procedure:
33 Accurately weigh 0.1000 g of platinum metal, 99.9%
Pt (m/m), into a 50 ml beaker. Add a minimum volume of
50% (v/v) aqua regia (paragraph 31), heat on a hotplate
(paragraph 45) in a fume cupboard and evaporate just to
dryness. Add 5 ml of concentrated hydrochloric acid
(paragraph 26) and again evaporate to dryness. Dissolve
the residue in 20 ml 1 + 1 hydrochloric acid (paragraph
28), remove the beaker from the hotplate, allow to cool,
and quantitatively transfer the solution into a 100 ml
volumetric flask. Finally, dilute to the mark with water
(paragraph 25), stopper and mix thoroughly.
Note 5: Platinum standard solution prepared according to
the instructions in paragraph 33 may be stored in a plastic
bottle (paragraph 42) for a period of one year without
deterioration.
WARNING - Soluble platinum compounds are potent in
producing skin and respiratory sensitisation. Great care
should be taken when working with platinum compounds
and solutions containing platinum.
4
Laboratory detergent solution
35 A laboratory grade detergent suitable for cleaning of
samplers and laboratory glassware, diluted with water
(paragraph 25) according to the manufacturer’s
instructions.
SAMPLING EQUIPMENT
Samplers for collection of the inhalable fraction of
the airborne particles
36 Samplers, with protective covers, for collection of the
inhalable fraction of the airborne particles, as defined in
European Standard EN 481.11 Inhalable dust samplers
suitable for personal sampling are described in
MDHS 14/2.12
Note 6: In general, the collection characteristics of
inhalable samplers can be such that particulate material
collected on the filter is the inhalable fraction of the
airborne particles, and any deposited on the internal
surfaces of the sampler is not of interest. However, some
samplers are designed such that airborne particles which
pass through the entry orifice(s) constitute the inhalable
fraction, in which case any particulate material deposited
on the internal surfaces of the sampler is part of the
sample. Samplers of this type incorporate an internal filter
cassette which may be removed from the sampler to
enable this material to be easily recovered. Refer to the
manufacturer’s instructions to ascertain what constitutes
the inhalable fraction of the sample.
Note 7: Samplers manufactured in non-conducting
material have electrostatic properties which may
influence representative sampling. Electrostatic
influences should be reduced, where possible, by using
samplers manufactured from conducting material.
Filters
37 Filters, of a diameter suitable for use in the samplers
(paragraph 36), with a retentivity of not less than 99.5%
for particles with a 0.3 µm diffusion diameter. The use of
filters that are soluble using the sample preparation
procedure described is recommended, and mixed
cellulose ester filters of 0.8 µm mean pore diameter are
considered to be most suitable.
Note 8: Glass fibre or other filters which do not dissolve
using the sample preparation procedure described may
be used, but extra care needs to be taken to ensure
quantitative transfer of sample solutions to volumetric
flasks (paragraph 76).
Sampling pumps
38 Sampling pumps, complying with the provisions of
draft European Standard prEN1232,13 with an adjustable
flow rate, incorporating a flowmeter or a flow fault
indicator, capable of maintaining the selected flow rate
(see paragraph 54) to within ±5% of the nominal value
throughout the sampling period (see paragraph 55), and
capable of being worn by persons without impeding
normal work activity. The pumps shall give a pulsationfree flow (if necessary, a pulsation damper shall be
incorporated between the sampler and the pump, as near
to the pump as possible). Flow-stabilised pumps may be
required to maintain the flow rate within the specified
limits.
Flowmeter
39 Flowmeter, portable, capable of measuring the
appropriate flow rate (see paragraph 54) to within ±1%,
and calibrated against a primary standard.
Note 9: Flowmeters incorporated in sampling pumps are
not suitable for accurate measurement of the flow rate.
However, they can be useful for monitoring the
performance of samplers (see paragraph 59), provided
they have adequate sensitivity.
Ancillary equipment
40 Flexible plastic tubing, of a diameter suitable for
ensuring a leakproof fit, to connect the sampler to the
pump; a belt to which the pump can conveniently be
fixed, unless the pump is sufficiently small to fit in the
worker’s pocket; flat-tipped tweezers for loading and
unloading the filters into samplers; and filter transport
cassettes, or similar, to transport filters to the laboratory,
if transport in the samplers is impracticable.
Figure 1 Suction filtration apparatus
Disposable beakers, polypropylene
43 Disposable plastic beakers, as an alternative to 50 ml
glass beakers, for use in the 0.07 M hydrochloric acid
leach procedure for soluble platinum compounds.
LABORATORY APPARATUS
Suction filtration apparatus
Glassware, made of borosilicate glass
44 Suction filtration apparatus, for filtration of the 0.07 M
hydrochloric acid leach solution used in the sample
dissolution procedure for soluble platinum compounds
(paragraphs 71 to 74). Suitable apparatus comprises of a
water-operated or electrically driven vacuum pump,
connected to a conical flask fitted with a filter
funnel/support assembly (see Fig 1). Mixed cellulose
ester membrane filters, of a diameter suitable for use with
the apparatus, are also required.
41 A selection of laboratory glassware, including:
beakers; watch glasses; measuring cylinders; and onemark volumetric flasks, class A, complying with the
requirements of BS 1792.14
Note 10: It is recommended that a set of glassware is
reserved for the analysis of platinum by this method (see
paragraph 70).
Polypropylene bottle
42 A polypropylene bottle, with leakproof screw cap, for
storage of stock standard solution (paragraph 33),
cleaned before use by soaking in 1 + 9 nitric acid
(paragraph 30) for at least 24 hours and then rinsing
thoroughly with water (paragraph 25). A bottle made of
an alternative plastic may be used provided that it is
suitable for the intended use.
Note 11: Alternative suction filtration apparatus is
available which permits simultaneous vacuum filtration of
multiple samples.
Hotplate
45 A thermostatically controlled hotplate, capable of
maintaining the required surface temperatures.
Disposable gloves
46 Disposable gloves, impermeable, to avoid the
possibility of contamination from the hands and to protect
5
them from contact with toxic and corrosive substances.
PVC gloves are suitable.
SAMPLING
Sampling procedure
Filter paper
47 A hardened, ashless, cellulose (paper) filter of
medium filtering speed and retentivity.
Piston operated volumetric apparatus
48 A set of adjustable micropipettes, complying with the
requirements of BS 7653-1 to BS 7653-4,15-18 for the
preparation of solutions for calibration of the atomic
absorption spectrometer (paragraph 77), calibration of
the inductively coupled plasma-mass spectrometer
(paragraph 86) and dilution of samples (paragraphs 84
and 91). A suitable set might include micropipettes
covering the ranges 10 µl to 100 µl, 100 µl to 1000 µl
and 1000 µl to 5000 µl.
Atomic absorption spectrometer
49 An atomic absorption spectrometer equipped with a
platinum hollow cathode lamp.
Electrothermal atomiser
50 An electrothermal atomiser, fitted with a solid,
pyrolytic graphite platform mounted in a pyrolyticallycoated graphite tube, supplied with argon as a purge
gas, and equipped with an autosampler capable of
injecting microlitre volumes onto the platform.
Note 12: Some manufacturers of atomic absorption
spectrometers use an alternative design of
electrothermal atomiser to achieve a constant
temperature environment during atomisation, and some
use aerosol deposition as a means of sample
introduction. The use of such accessories is acceptable,
but the method performance could be different from that
described in paragraphs 15 to 18.
Inductively coupled plasma-mass spectrometer
51 An inductively coupled plasma-mass spectrometer,
normally equipped with a quadrupole mass
spectrometer, and an autosampler.
Disposable autosampler cups
52 Disposable polystyrene autosampler cups for use
with the electrothermal atomiser autosampler. Soak in
1 + 9 nitric acid (paragraph 30) before use.
Note 13: Disposable polystyrene autosampler cups are
also useful for containing solutions to be pipetted in
microlitre quantities.
Disposable autosampler tubes
53 Disposable polystyrene autosampler tubes for use
with the inductively coupled plasma-mass spectrometer
autosampler.
6
54 Use the samplers (paragraph 36) at the design flow
rate, so that they exhibit the required collection
characteristics. Refer to the manufacturer’s instructions.
55 Select a suitable sampling time, such that the filter
does not become overloaded with aerosol. (An 8-hour
time weighted average concentration may be derived
from the results for two or more consecutive samples, as
described in Guidance Note EH 42.9)
Preparation of sampling equipment
56 Clean the samplers (paragraph 36) before use.
Disassemble the samplers, soak in laboratory detergent
solution (paragraph 35), rinse thoroughly with water
(paragraph 25), wipe with absorptive tissue and allow to
dry thoroughly before reassembly. Alternatively, use a
laboratory washing machine.
Perform the following in an area where platinum
contamination is known to be low, and wear disposable
gloves (paragraph 46) to prevent the possibility of
contamination.
57 Load the filters (paragraph 37) into clean, dry
samplers (see paragraph 56) using clean, flat-tipped
tweezers (paragraph 40). Connect each loaded sampler
to a sampling pump (paragraph 38) using plastic tubing
(paragraph 40), ensuring that no leaks can occur. Switch
on the pump, attach the calibrated flowmeter (paragraph
39) to the sampler so that it measures the flow through
the sampler inlet orifice, and set the appropriate flow rate
(see paragraph 54) with an accuracy of ±5%. Switch off
the pump and seal the sampler with its protective cover
to prevent contamination with platinum during transport
to the sampling position.
Note 14: It might be necessary to allow the pump to
operate for an appropriate period to enable it to warm up
and the flow rate to stabilise (refer to the manufacturer’s
recommendations). If this is the case, discard the used
filter after the warm-up period and load a new one into
the sampler for collection of the sample. Then attach the
calibrated flowmeter again and readjust the flow rate to
the appropriate value (see paragraph 54) with an
accuracy of ±5%.
Collection of samples
58 Fix the sampler to the lapel of the worker, in the
breathing zone and as close to the mouth and nose as
practicable. Then, either place the sampling pump in a
convenient pocket or attach it to the worker in a manner
that causes minimum inconvenience, eg to a belt
(paragraph 40) around the waist. When ready to begin
sampling, remove the protective cover from the sampler
and switch on the pump. Record the time at the start of
the sampling period, and if the pump is equipped with an
elapsed time indicator, set this to zero.
59 Since it is possible for a filter to become clogged,
monitor the performance of the sampler frequently, a
minimum of once per hour. Measure the flow rate with an
accuracy of ±5% using the calibrated flowmeter
(paragraph 39) and record the measured value.
Terminate sampling and consider the sample to be
invalid if the flow rate is not maintained to within ±5% of
the nominal value throughout the sampling period.
the samplers in which they were collected.
Note 15: Regular observation of the flow fault indicator
is an acceptable means of ensuring that the flow rate of
flow-stabilised sampling pumps is maintained
satisfactorily, provided that the flow fault indicator
indicates malfunction when the flow rate is outside ±5%
of the nominal value.
ANALYSIS
60 At the end of the sampling period (see paragraph
55), measure the flow rate with an accuracy of ±5%
using the calibrated flowmeter (paragraph 39), switch off
the sampling pump, and record the flow rate and the
time. Also observe the reading on the elapsed time
indicator, if fitted, and consider the sample to be invalid if
the reading on the elapsed time indicator and the timed
interval between switching on and switching off the
sampling pump do not agree to within ±5%, since this
may suggest that the sampling pump has not been
operating throughout the sampling period. Reseal the
sampler with its protective cover and disconnect it from
the sampling pump.
67 Before use, clean all glassware (paragraph 41) to
remove any residual grease or chemicals. Firstly soak
overnight in laboratory detergent solution (paragraph 35)
and then rinse thoroughly with water (paragraph 25).
Alternatively, use a laboratory washing machine.
61 Carefully record the sample identity and all relevant
sampling data (see Appendix A). Calculate the mean
flow rate by averaging the flow rate measurements taken
throughout the sampling period and calculate the volume
of air sampled, in litres, by multiplying the flow rate in
litres per minute by the sampling time, in minutes.
62 With each batch of ten samples, submit for analysis
two unused filters from the same lot of filters used for
sample collection. Subject these blank filters to exactly
the same handling procedure as the samples, but draw
no air through them.
66 Transport the filter transport cassettes (see
paragraph 63), sampler filter cassettes (see paragraph
64) or samplers (see paragraph 65) to the laboratory in a
container which has been designed to prevent damage
to samples in transit and which has been labelled to
assure proper handling.
Wear disposable gloves (paragraph 46) during analysis to
protect the hands from corrosive and oxidising reagents.
Cleaning of glassware
68 After initial cleaning (paragraph 67), clean all
beakers used in the sample dissolution procedure
(paragraphs 71 to 76) with hot nitric acid. Fill to one third
capacity with concentrated nitric acid (paragraph 29),
cover with a watch glass, heat to approximately 150°C
on the hotplate (paragraph 45) in a fume cupboard for
1 hour, allow to cool, and then rinse thoroughly with
water (paragraph 25).
69 After initial cleaning (paragraph 67), clean all
glassware other than beakers used in the sample
dissolution procedure by soaking in 1 + 9 nitric acid
(paragraph 30) for at least 24 hours and then rinsing
thoroughly with water (paragraph 25).
70 Glassware which has been previously subjected to
the cleaning procedure described in paragraphs 67 to
69, and which has been reserved for determination of
platinum by this method, can be adequately cleaned by
rinsing thoroughly with 1 + 9 nitric acid (paragraph 30)
and then with water (paragraph 25).
Transportation
Preparation of sample and blank solutions
Perform the following in an area where platinum
contamination is known to be low.
63 For samplers which collect the inhalable fraction of
airborne particles on the filter (see note 6), remove the
filter from each sampler using clean flat-tipped tweezers
(paragraph 40), place in a labelled filter transport
cassette (paragraph 40) and close with a lid.
64 For samplers which have an internal filter cassette
(see note 6), remove the filter cassette from each
sampler, fasten with the transport clip supplied by the
manufacturer, and label appropriately.
65 For samplers designed such that airborne particles
which pass through the entry orifice(s) constitute the
inhalable fraction but which do not have an internal filter
cassette (see note 6), and for samplers of the disposable
cassette type, transport the samples to the laboratory in
71 Open the filter transport cassettes (see paragraph
63), sampler filter cassettes (see paragraph 64) or
samplers (see paragraph 65) and transfer each filter into
an individual, labelled 50 ml beaker (paragraph 41) or a
disposable plastic beaker (paragraph 43) using clean
flat-tipped tweezers (paragraph 40). Follow the same
procedure for the blank filters (paragraph 62).
72 If the sampler used was of a type in which airborne
particles deposited on the internal surfaces of the filter
cassette or sampler form part of the sample (see note 6),
wash any particulate material adhering to the internal
surfaces into the beaker using an aliquot of the 5 ml of
0.07 M hydrochloric acid used to leach the sample filters
(see paragraph 73).
73 Add 5 ml of 0.07 M hydrochloric acid (paragraph 27)
to each beaker, cover with a watch glass, place on the
7
orbital mixer or other mechanical shaking device and
agitate for 30 minutes to dissolve the soluble platinum
species. Alternatively, use an ultrasonic bath. Ensure that
the sample filters are fully immersed throughout the leach
period.
78 Prepare a working calibration blank solution following
the procedure in paragraph 77, but omitting the 500 µl of
working standard platinum solution.
74 Filter each leach solution through a mixed cellulose
ester membrane filter using suction filtration apparatus
(paragraph 44), collecting the filtrate in an individual,
labelled test tube (see Fig 1). Transfer the sample filter to
the filtration apparatus, rinse the sample filter and beaker
with three 1 ml aliquots of 0.07 M hydrochloric acid,
allowing the solution to completely drain from the filter
funnel between washings. Quantitatively transfer the
filtrate to a 10 ml volumetric flask, rinsing out the test tube
with a further 1 ml of 0.07 M hydrochloric acid. Finally,
dilute to the mark with 0.07 M hydrochloric acid, stopper
and mix thoroughly.
79 Set up the atomic absorption spectrometer
(paragraph 49) and electrothermal atomiser (paragraph
50) to determine platinum at a wavelength of 265.9 nm
using background correction. Follow the manufacturer’s
recommendations for specific operating parameters.
75 If applicable (see paragraph 23), retain the sample
filter and the secondary filter (the membrane filter used for
filtration of the leach solution) for subsequent analysis for
platinum metals.
76 Using flat-tipped tweezers transfer the sample filter
and the secondary filter used for filtration of the leach
solution (if applicable) into a 50 ml low form beaker, add
10 ml of 50% (v/v) aqua regia (paragraph 31) and cover
with a watch glass. Place on a hotplate (paragraph 45),
heat to dissolve the filters and then evaporate just to
dryness. Redissolve in 2 ml of concentrated hydrochloric
acid (paragraph 26) and repeat the evaporation twice.
Allow to cool, add 5 ml 0.07 M hydrochloric acid
(paragraph 27), and heat to dissolve the residue. Carefully
rinse the watch glass and the sides of each beaker with
0.07 M hydrochloric acid (paragraph 27) and quantitatively
transfer the solution to an individual, labelled 10 ml
volumetric flask. If necessary, remove any undissolved
particulate material by filtering through a cellulose (paper)
filter (paragraph 47) which has been pre-washed with
0.07 M hydrochloric acid. Finally dilute to the mark with
0.07 M hydrochloric acid, stopper and mix thoroughly.
Analysis by electrothermal atomic absorption
spectrometry
Note 16: It is essential that strict standards of cleanliness
are observed to avoid contamination of labware when
carrying out electrothermal atomic absorption
spectrometry, since the technique exhibits a very low
detection limit. Ensure that all glassware is cleaned
thoroughly before use in accordance with paragraphs 67
to 70, and that autosampler cups (paragraph 52) are
stored in 1 + 9 nitric acid (paragraph 30) until required.
Preparation of working calibration solutions
77 Prepare a working calibration solution at a
concentration of 500 ng ml-1 of platinum. Accurately
pipette 500 µl of working standard platinum solution
(paragraph 34) into a 100 ml volumetric flask and dilute to
the mark with 0.07 M hydrochloric acid (paragraph 27),
stopper and mix thoroughly. Prepare this solution fresh
weekly.
8
Atomic absorption measurements
Note 17: The operating parameters for electrothermal
atomic absorption spectrometry vary considerably
between different instruments, much more so than for
flame atomic absorption spectrometry. A Perkin-Elmer
5100PC atomic absorption spectrometer with Zeeman
HGA-600 graphite furnace module and AS-60
autosampler was used in the validation of this method,5
and the operating parameters used are given in Appendix
B. The characteristic mass for platinum, defined as the
number of picograms required to give 0.0044 absorbanceseconds, was determined to be 100 pg for this analytical
system. This is equivalent to a sample solution
concentration of 5 ng ml-1 of platinum for a 20 µl sample
solution injection volume.
80 Program the autosampler to prepare calibration
solutions in situ on a pyrolytic graphite platform mounted
in the pyrolytically-coated graphite tube of the
electrothermal atomiser. Prepare at least six calibration
solutions to cover the range 0 ng ml-1 to 500 ng ml-1 using
the working calibration solution (paragraph 77) and the
working calibration blank solution (paragraph 78). See
Table 2 for typical autosampler injection volumes.
Note 18: The procedure described above may be varied
to accommodate the use of electrothermal atomisers of
alternative design (see note 12).
Note 19: Calibration and test solutions may be prepared
in volumetric flasks as an alternative to preparation in situ
using the autosampler.
81 Set up the analytical sequence in the microprocessor
or personal computer. Specify an appropriate number of
replicate analyses for each solution, and insert a
calibration blank solution and a mid-range calibration
solution after each five to ten sample solutions to monitor
for baseline drift and sensitivity change respectively.
82 Place the working calibration solution (paragraph 77),
the working calibration blank solution (paragraph 78), and
the sample and blank solutions (paragraphs 74 and 76) in
separate acid-washed autosampler cups (paragraph 52)
and position as appropriate in the autosampler carousel.
Analyse the calibration, sample and blank solutions, using
the microprocessor or personal computer software to
generate a calibration and obtain a direct read-out of
sample and blank results in ng ml-1 of platinum.
83 If significant baseline drift is observed during the
course of the analysis, or if the sensitivity changes by
more than ±5%, take one of the following appropriate
corrective measures: either use the available software
facilities of the microprocessor or personal computer to
correct for the sensitivity change (reslope facility); or
suspend analysis and recalibrate the spectrometer as
described in paragraph 82. In either case reanalyse the
solutions which were analysed during the period in which
the sensitivity change occurred.
84 If concentrations of platinum above the upper limit of
the calibration range are found, dilute the sample solutions
to bring them within the calibration range, and repeat the
analysis. Make all dilutions so that the final hydrochloric
acid concentration is 0.07 M. Record the dilution factor.
85 Calculate the mean platinum concentration of the
blank solutions.
Analysis by inductively coupled plasma-mass
spectrometry
Note 20: It is essential that strict standards of cleanliness
are observed to avoid contamination of labware when
carrying out inductively coupled plasma-mass
spectrometry, since the technique exhibits extremely low
detection limits. Ensure that all glassware is cleaned
thoroughly before use in accordance with paragraphs 67
to 70.
Preparation of calibration solutions
86 Prepare at least six calibration solutions to cover the
range 0 ng ml-1 to 500 ng ml-1 of platinum. Accurately
pipette the appropriate volumes of working standard
platinum solution (paragraph 34) into separate, labelled
100 ml volumetric flasks. Dilute to the mark with 0.07 M
hydrochloric acid (paragraph 27), stopper and mix
thoroughly. Prepare these solutions fresh daily.
87 Set up the inductively coupled plasma-mass
spectrometer (paragraph 51) to determine platinum at a
mass of 195 (other masses may also be used). Follow the
manufacturer’s recommendations for specific operating
parameters.
Note 21: The operating parameters for inductively
coupled plasma-mass spectrometry vary considerably
between different instruments. A Perkin-Elmer Elan 5000
inductively coupled plasma-mass spectrometer was used
in the validation of this method,5 and the operating
parameters used are given in Appendix C.
88 Set up the analytical sequence in the microprocessor
or personal computer. Specify an appropriate number of
replicate analyses for each solution, and insert a
calibration blank solution and a mid-range calibration
solution after each five to ten sample solutions to monitor
for instrumental drift and sensitivity change respectively.
89 Place the calibration solutions (paragraph 86) and the
sample and blank solutions (paragraphs 74 and 76) in
separate acid-washed autosampler tubes (paragraph 53)
and position as appropriate in the autosampler tray.
Analyse the calibration, sample and blank solutions, and
use the instrument’s computer software to generate a
calibration and obtain a direct read-out of sample and
blank results in ng ml-1 of platinum.
90 If significant instrumental drift is observed during the
course of the analysis, take one of the following
appropriate corrective measures: either use available
computer software facilities to correct for the sensitivity
change (reslope facility); or suspend analysis and
recalibrate the spectrometer as described in paragraph 89.
In either case reanalyse the solutions which were
analysed during the period in which the sensitivity change
occurred. An internal standard element may also be added
to all solutions to correct for drift in sensitivity.
91 If concentrations of platinum above the upper limit of
the calibration range are found, dilute the sample solutions
to bring them within the calibration range, and repeat the
analysis. Make all dilutions so that the final hydrochloric
acid concentration is 0.07 M. Record the dilution factor.
92 Calculate the mean platinum concentration of the
blank solutions.
QUALITY CONTROL MEASURES
93 Analytical quality requirements, guidance on the
establishment of a quality assurance programme and
details of internal quality control and external quality
assessment schemes are fully described in MDHS 71.19
94 If platinum analysis is performed frequently it is
recommended that internal quality control is performed. In
such instances, prepare quality control filters by spiking a
large batch of filters with microlitre volumes of a solution of
known platinum concentration. Analyse a random selection
of at least 20 filters, each along with a different analytical
batch, and calculate the mean value and standard
deviation of the readings. Assuming that the distribution of
these values is Gaussian, construct a Shewhart chart with
warning and action limits at ± 2SD and ±3SD respectively.
Subsequently, analyse a quality control filter with each
analytical batch and plot the result on the Shewhart chart.
Compare the internal quality control result with the target
value and take appropriate action if the warning or action
limits are exceeded, as recommended in MDHS 71.19
95 It is strongly recommended that all laboratories
undertaking the determination of toxic elements in
workplace air should participate in an external quality
assessment scheme such as HSE’s Workplace Analysis
Scheme for Proficiency (WASP). Details of WASP are
given in MDHS 71.19 However, at present the WASP
scheme does not encompass platinum.
CALCULATIONS
Volume of air sample
96 Calculate the mean flow rate during the sampling
period by averaging the flow rate measurements taken at
the start and end of the sampling period. Then calculate
the volume, in litres, of the air sample by multiplying the
mean flow rate, in litres per minute, by the sampling time,
in minutes.
9
Concentration of platinum in air
97 Calculate the concentration of platinum in air, ρ(Pt), in
micrograms per cubic metre (µg m-3), using the equation:
ρ(Pt)
[ρ(Pt)1.V1.DF1-ρ(Pt)0.V0.DF0]
(g) the time at the start and at the end of the sampling
period, and the sampling time in minutes;
(h) the volume of air sampled, in litres;
(i) the name of the person who collected the sample;
=
(j) the time-weighted average mass concentration of
platinum found in the air sample, in micrograms per
cubic metre;
V
where
ρ(Pt)0 is the mean concentration, in ng ml-1, of platinum in
the blank solutions (see paragraphs 85 and 92);
(k) the name of the analyst;
(l) the date of the analysis.
ρ(Pt)1 is the concentration, in ng ml-1, of platinum in the
sample solution (see paragraphs 82 and 89);
V
is the volume, in litres, of the air sample (see
paragraph 96);
V0
is the volume, in ml, of the blank solutions, ie 10 ml
(see paragraphs 74 and 76);
V1
is the volume, in ml, of the sample solution, ie 10 ml
(see paragraphs 74 and 76);
DF0
is the dilution factor for the blank solutions, ie 1;
and
DF1
is the dilution factor for the sample solutions (see
paragraphs 84 and 91).
APPENDIX B
TYPICAL OPERATING PARAMETERS
FOR DETERMINATION OF PLATINUM BY
ELECTROTHERMAL ATOMIC ABSORPTION
SPECTROMETRY
Mode:
Integration time:
Background correction:
Injection volumes:
Peak area
10 seconds
Zeeman
20 µl of calibration, sample or
blank solution
Table 1 Typical temperature profile for determination of
platinum using electrothermal atomic absorption
spectrometry
TEST REPORT
Step
Ramp
time
(sec)
Hold
time
(sec)
1 Dry
50
10
125
300
2 Ash
25
5
1300
300
3 Cool down
1
15
20
300
4 Atomise
0
10
2700
0
5 Clean
1
5
2750
300
98 Appendix A gives recommendations for information to
be included in the test report.
APPENDIX A
REPORT
RECOMMENDATIONS FOR THE TEST
It is recommended that the test report should include the
following information:
(a) a complete identification of the air sample, including
the date of sampling, the place of sampling, and the
identity of the individual whose breathing zone was
sampled;
(b) a reference to this MDHS, including information about
which sample dissolution method and which analytical
technique were used, and a description of any
deviation from the procedures described;
(c) the type and diameter of filter used;
(d) the type of sampler used;
(e) the type of sampling pump used;
(f) the type of flowmeter used, the primary standard
against which it was calibrated, and the range of flow
rates for which the flowmeter was calibrated;
10
Furnace Argon
Read
temp
flow
(°C)
(ml min-1)
*
Table 2 Typical autosampler injection volumes for the in-situ preparation of calibration, sample and blank solutions
Volume of
working calibration
solution (µl)
Volume of working
calibration blank
solution (µl)
Volume of
sample or blank
solution (µl)
0 ng ml-1 calibration solution
-
20
-
100 ng ml-1 calibration solution
4
16
-
200 ng ml-1 calibration solution
8
12
-
300 ng ml-1 calibration solution
12
8
-
400 ng ml-1 calibration solution
16
4
-
500 ng ml-1 calibration solution
20
-
-
Sample or blank solution
-
-
20
Sample solution dilution
-
(20 - x)
x
APPENDIX C
TYPICAL OPERATING PARAMETERS
FOR DETERMINATION OF PLATINUM BY
INDUCTIVELY COUPLED PLASMA-MASS
SPECTROMETRY
RF generator power
Plasma gas flow rate
Auxiliary gas flow rate
Nebuliser gas flow rate
Dwell time
Sweeps/reading
Replicate time
Scanning mode
Number of replicates
Points/spectral peak
Resolution
Atomic mass measured
Internal standard
1000 watts
15 l min-1
1 l min-1
0.95 l min-1
40 ms
50
2000 ms
Peak hop
5
1
Normal
195
Not used
5
J M Usher, S Roche, S D Bradley and A M Howe
Validation of the dissolution procedure for the
determination of platinum metal and soluble platinum
compounds in air using electrothermal atomic absorption
spectrometry and inductively coupled plasma mass
spectrometry HSL Internal Report IS/96/07 1996
6 British Standards Institution Workplace atmospheres:
general requirements for the performance of procedures
for the measurement of chemical agents BS EN 482
BSI 1994 ISBN 0 580 23644 7
7 Control of Substances Hazardous to Health
Regulations 1994 SI 1994/3246 HMSO 1994
ISBN 0 11 043721 7
8 Health and Safety Commission Approved Codes of
Practice: Control of Substances Hazardous to
Health/Control of Carcinogenic Substances/Control of
Biological Agents HSE Books 1995 ISBN 0 7176 0819 0
REFERENCES
1 Health and Safety Executive, Methods for the
Determination of Hazardous Substances Platinum metal
and soluble inorganic compounds of platinum in air:
laboratory method using carbon furnace atomic absorption
spectrometry MDHS 46 HSE Books 1985
ISBN 0 11 885635 9
2 Health and Safety Executive Platinum metal and
soluble platinum salts: criteria document for an
occupational exposure limit EH 65/24 HSE Books 1996
ISBN 0 7176 1055 1
3 Health and Safety Executive, Environmental Hygiene
Series Guidance Note Occupational exposure limits EH 40
HSE Books (updated annually)
9 Health and Safety Executive, Environmental Hygiene
Series Guidance Note Monitoring strategies for toxic
substances EH 42 HSE Books 1989 ISBN 0 11 885412 7
10 British Standards Institution Water for analytical
laboratory use: specification and test methods
BS EN ISO 3696 1995 BSI 1987
11 British Standards Institution Workplace atmospheres:
size fraction definitions for measurement of airborne
particles BS EN 481 BSI 1993
12 Health and Safety Executive, Methods for the
Determination of Hazardous Substances General methods
for the gravimetric determination of respirable and total
inhalable dust MDHS 14/2 HSE Books 1997
ISBN 0 7176 1295 3
4 Control of Substances Hazardous to Health
(Amendment) Regulations 1996 (forthcoming)
11
13 Comité Européen de Normalization Workplace
atmospheres: pumps for personal sampling of chemical
agents - requirements and test methods prEN 1232 CEN
1995
14 British Standards Institution Laboratory glassware:
one-mark volumetric flasks BS 1792 BSI 1982
15 British Standards Institution Piston and/or plunger
operated volumetric apparatus (POVA) Part 1: Glossary of
terms BS 7653-1 BSI 1993
ADVICE
Advice on this method and the equipment used can be
obtained from the Health and Safety Executive, Health
and Safety Laboratory, Broad Lane, Sheffield, S3 7HQ
(tel: 0114 289 2000).
The Health and Safety Executive wishes, wherever
possible, to improve the methods described in this series.
Any comments that might lead to improvements would
therefore be welcome and should be sent to the above
address.
16 British Standards Institution Piston and/or plunger
operated volumetric apparatus (POVA) Part 2: Methods of
operation BS 7653-2 BSI 1993
17 British Standards Institution Piston and/or plunger
operated volumetric apparatus (POVA) Part 3: Methods of
test BS 7653-3 BSI 1993
18 British Standards Institution Piston and/or plunger
operated volumetric apparatus (POVA) Part 4:
Specification for conditions of test, safety and supply
BS 7653-4 BSI 1993
19 Health and Safety Executive, Methods for the
Determination of Hazardous Substances Analytical quality
in workplace air monitoring MDHS 71 HSE Books 1991
ISBN 0 11 885976 5
©Crown copyright 1996
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